WS-19 Crystal Calibrator Dog Bone Question
 

It’s my understanding that there wasn’t a crystal calibrator for the MkII WS-19, only the MkIII. Since we can all agree the MkII uses a 6pt dog bone from the PSU to the main set and MkIII uses a 12pt dog bone, then what is this, and can it be repaired to work properly? By the way, I’ve seen this one, or an eerily similar to this one, on eBay before.

Hi James.

This is a regular item on eBay and was covered some time ago here on MLU.

It is what is left of a Crystal Calibrator Power Cord Assembly for use on a Mk II 19-Set. Somebody has cut off the brown ID Collar that was around the wire loom, opposite the exit side for the calibrator feed line, and the line itself. My guess would be somebody wanted a simple 6-pin Mk II dog bone and did not realize what a rare piece of kit they were hacking up.

All Crystal Calibrator kits were issued with the calibrator, a 6-Pin dog bone connector, a 12-Pin dog bone connector, and a slow motion drive and manual.

The slow motion drive was to be used on a Mk II 19-Set to replace the standard drive on the Tuning Dial. All unused parts were to be returned to Stores.

I checked with the seller of this one last year and it came into his possession in this condition.

David

Thanks, David. How would one go about repairing it?

You would need a suitable length of 3-core braid-screened cable (like the kind that has been cut off) and the correct 3-pin Jones connector to match the plug on the calibrator front panel.

Then it's just a (simple?) matter of making up the new flying lead and fitting it to the existing cable - making sure you get the 12V and 250V connections correct.

Best regards,
Chris.

There's even a 12pt-6pt variant with the calibrator lead, for use with sets modified to run from the later (Canadian No.2, British twin dynamotor, Eicor dynamotor, or the AC Supply Unit Rectifier No.1) supply units.

Other variant power supply to set cables include the RF Amplifier No.2 control cable (with HT2 brought out to a 2-pin socket so that the amplifier control relay can be inserted in series) - which again exists in 6-6, 12-6 and 12-12 variants, and a _very_ confusing to the unwary 12-12 lookalike that has the 2-pin socket connected to the +12-volt set (valve heaters and relay) supply and ground - this was for running the Power Supply and L.F. Amplifier units (1, 2 or 3) for the WS38, 88 or 31 AFV variants in AFVs - usually in conjunction with the Canadian Supply Unit No.2 to provide 12V from a 2-wire 24 volt supply in later tanks. (If you try using that particular cable on the RF amplifier it switches the amplifier to 'Send' and it stays there - the 12V won't damage the control relay but seriously confuses the owner!)

Best regards,
Chris.

A further thought: it's possible that you could use modern flat 'earth braid' and slide suitable 3-core cable inside it. The result is likely to look a bit 'too new', though.

On a different note, I suspect the calibrators were only issued to Net control stations (i.e. with actual signals personnel) during WW2, and the lower level users simply netted to 'Control'. Using the calibrator is not that simple, and it's just one more thing to go wrong, so may have been 'dedicated wireless trucks only' issue.

Best regards,
Chris.